Added tracing to data-manager's loading of resources.

chrome/browser/ui/webui/chrome_url_data_manager_backend.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/chrome_url_data_manager_backend.h"
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
+#include "base/debug/trace_event.h"
 #include "base/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
 #include "chrome/browser/net/chrome_url_request_context.h"
 #include "chrome/browser/ui/webui/shared_resources_data_source.h"
 #include "chrome/common/chrome_paths.h"
@@ skipping 199 matching lines @@
       backend_(backend),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
   DCHECK(backend);
 }
 
 URLRequestChromeJob::~URLRequestChromeJob() {
   CHECK(!backend_->HasPendingJob(this));
 }
 
 void URLRequestChromeJob::Start() {
+  TRACE_EVENT_ASYNC_BEGIN1("browser", "DataManager:Request", this, "URL",
+      request_->url().possibly_invalid_spec());
+
   // Start reading asynchronously so that all error reporting and data
   // callbacks happen as they would for network requests.
   MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&URLRequestChromeJob::StartAsync,
                  weak_factory_.GetWeakPtr()));
 }
 
 void URLRequestChromeJob::Kill() {
   backend_->RemoveRequest(this);
 }
 
 bool URLRequestChromeJob::GetMimeType(std::string* mime_type) const {
   *mime_type = mime_type_;
   return !mime_type_.empty();
 }
 
 void URLRequestChromeJob::GetResponseInfo(net::HttpResponseInfo* info) {
   DCHECK(!info->headers);
   // Set the headers so that requests serviced by ChromeURLDataManager return a
   // status code of 200. Without this they return a 0, which makes the status
   // indistiguishable from other error types. Instant relies on getting a 200.
   info->headers = new net::HttpResponseHeaders("HTTP/1.1 200 OK");
   AddContentSecurityPolicyHeader(request_->url(), info->headers);
 }
 
 void URLRequestChromeJob::DataAvailable(RefCountedMemory* bytes) {
+  TRACE_EVENT_ASYNC_END0("browser", "DataManager:Request", this);

[flackr, 2012/04/12 15:04:05]

If there's any significant amount of work done in this method (i.e. by
CompleteRead) then maybe this signal should be at the end of the method.

   if (bytes) {
     // The request completed, and we have all the data.
     // Clear any IO pending status.
     SetStatus(net::URLRequestStatus());
 
     data_ = bytes;
     int bytes_read;
     if (pending_buf_.get()) {
       CHECK(pending_buf_->data());
       CompleteRead(pending_buf_, pending_buf_size_, &bytes_read);
@@ skipping 284 matching lines @@
 
   return new URLRequestChromeJob(request, backend_);
 }
 
 }  // namespace
 
 net::URLRequestJobFactory::ProtocolHandler*
 CreateDevToolsProtocolHandler(ChromeURLDataManagerBackend* backend) {
   return new DevToolsJobFactory(backend);
 }